Heart Defects (Congenital) in Dogs

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Last updated on
4 min read

Key takeaways

Congenital heart defects are abnormalities of the heart that are present at birth.

  • Development of the heart structures and function in the unborn puppy may be defective due to genetic predisposition, environmental factors in the womb, or infection
  • Heart defects disrupt normal blood flow through the heart, which results in heart murmurs due to turbulence
  • There are a variety of different defects with differing symptoms and prognoses
  • Congenital heart defects can be life-threatening, and puppies with severe defects may be stillborn or die shortly after birth
  • Puppies that survive may show signs of cardiovascular distress, such as cyanosis, pale mucous membranes, weakness and failure to thrive
  • Some heart defects have more subtle or no visible effects and are not detected until a veterinarian discovers a heart murmur
  • Some puppies with mild defects live a normal life
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A closer look: Heart Defects (Congenital) in Dogs

Veterinary examination is required to diagnose the type and extent of heart defect(s). Early detection is important; without early diagnosis and treatment, heart defects that were not immediately fatal may still cause heart damage, heart failure, and death. Congenital heart defects can be life-threatening. Severe defects commonly cause stillbirth or sudden death.

There are different types of heart defects, which may affect the blood vessels, valves, septum or other structures of the heart. More than one defect may be present.

Common types of congenital heart defect include:

  • Patent ductus arteriosus (PDA)
  • Pulmonic stenosis
  • Aortic stenosis
  • Persistent right aortic arch
  • Ventricular septal defect (VSD)

Less common types include:

  • Tetralogy of Fallot
  • Atrial septal defect
  • Persistent left cranial vena cava
  • Mitral valve dysplasia
  • Tricuspid dysplasia
  • Cor triatriatum dexter

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Risk factors

Symptoms of congenital heart defects vary in severity and depend on the type of defect. Severe heart defects may be fatal. Serious defects may require surgery, while less severe conditions may have no or few other symptoms and no effect on lifespan.

Possible causes

Abnormalities in the structure of the heart may be the result of:

  • Genetic predisposition (inherited)
  • Environmental conditions
  • Infections
  • Poisoning
  • Medication taken by the mother
  • Poor nutrition of the mother during pregnancy

Main symptoms

Mild defects may present with no symptoms.

Testing and diagnosis

Diagnosis of congenital heart defects includes:

  • Physical examination, including auscultation to check for heart murmurs
  • Electrocardiography
  • X-rays
  • Echocardiography (ultrasound)
  • Blood work

Steps to Recovery

Treatment for heart defects depends on the type and the severity of the condition. Mild cases may not require any treatment, while in other cases medication may be prescribed to control symptoms of cardiovascular dysfunction. Surgical repair of the defect may be an option. Referral to a veterinary cardiologist may be required.

Congenital heart defects are lifelong conditions, but can sometimes be corrected or improved with surgery.


Congenital heart defects are present at birth. Prenatal veterinary care for the mother may prevent abnormalities related to the mother’s health and nutrition. Heart defects are not contagious, but may be inherited by offspring. Dogs with heart defects should not be bred.

Are Heart Defects (Congenital) in Dogs common?

Congenital heart defects are rare, but specific conditions may be more prevalent in certain breeds. Dogs with heart defects should not be bred, since heart defects may be due to genetic factors.

Typical Treatment

Treatment varies depending on the type and severity of the heart defect(s) and may include:

  • Heart or vascular surgery
  • Medication
  • Bloodletting (to treat polycythemia)


Sandra P. Tou , DVM, DACVIM-Cardiology, DACVIM-SAIM - Writing for Merck Veterinary Manual
Mark Rishniw, BVSc, PhD, DACVIM (SA-IM), DACVIM (CA) - Writing for Veterinary Partner
Mark Rishniw, BVSc, PhD, DACVIM (SA-IM), DACVIM (CA) - Writing for Veterinary Partner
Sandra P. Tou , DVM, DACVIM-Cardiology, DACVIM-SAIM - Writing for Merck Veterinary Manual
Henry Green III, DVM, DACVIM - Writing for dvm360®
Joan Capuzzi, VMD - Writing for dvm360®
Sandra P. Tou , DVM, DACVIM-Cardiology, DACVIM-SAIM - Writing for Merck Veterinary Manual

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